Field of the Invention
The present invention relates to wireless communication and, more particularly, to a CA method performed by a UE in a wireless communication system and a UE using the method.
Related Art
In International Telecommunication Union Radio communication sector (ITU-R), a standardization task for International Mobile Telecommunication (IMT)-Advanced, that is, a next-generation mobile communication system after the 3rd generation, is in progress. IMT-Advanced sets its goal to support Internet Protocol (IP)-based multimedia services at a data transfer rate of 1 Gbps in the stop and slow-speed moving state and of 100 Mbps in the fast-speed moving state.
The 3rd generation partnership project (3GPP) is a system standard to satisfy the requirements of IMT-Advanced and prepares LTE-advanced improved from long term evolution (LTE) based on orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission schemes. LTE-Advanced is one of strong candidates for IMT-Advanced.
An LTE-A system adopts a carrier aggregation (CA). In this case, the CA means that reception and transmission are performed by aggregating a plurality of component carriers (CCs). A CC may be divided into a primary component carrier (PCC) and a secondary component carrier (SCC). The PCC may be called a primary cell (PCell). Furthermore, other CCs other than one primary CC (PCC) may be defined as secondary CCs (SCCs). The SCC may be called a secondary cell (SCell). A UE may perform uplink transmission through a SCell.
A plurality of cells may be aggregated by a carrier aggregation (CA) scheme. For example, if many cell(s) have been configured according to the CA scheme, a total (E)PDCCH blind decoding (BD) number (e.g., a “total UE-specific search space (USS) number=a USS BD NUMBER×ACTIVATED CELL NUMBER FOR EACH CELL”) that needs to be performed by a UE is increased. Accordingly, an (E)PDCCH false detection probability (or number) is also increased.
Furthermore, for example, if a specific UE performs (E)PDCCH false detection-based erroneous PUCCH transmission, a (resource) collision against correct (or normal) PUCCH transmission performed by another UE at the same UL subframe (SF) point of time may be generated. This results in a performance reduction of the corresponding correct (or normal) PUCCH transmission.
Accordingly, the present invention proposes a method of reducing a (PUCCH) performance reduction attributable to (E)PDCCH false detection-based erroneous PUCCH transmission if many cell(s) have been configured according to the CA scheme.